Microray tube and frequency stabilizing system



Jan. 3, 1939. w. D. HERSHBERGER MICRORAY TUBE AND FREQUENCY STABILIZINGSYSTEM Filed July 50, 1936 M w r E 2 b 4 2 m G m 4 14044/4/1 D.Heesasnase Patented Jan. 3, 1939 UNITED STATES MICRORAY TUBE ANDFREQUENCY STABILIZING SYSTEM William D. Hcrshberger, Forth Monmouth,Oceanport, N. J.

Application July 30, 1936, Serial No. 93,462

11 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3'700. G. 757) The invention described herein may be manufactured and usedby or for the Government for governmental purposes, without the paymentto me of any royalty thereon.

This invention relates to micro-ray or ultra high frequency signalingsystems .and to an electron discharge device for use in such a system.

More particularly the invention proposes a device of this character forgenerating or producing electrical oscillations of ultra short wavelength.

An important object is to produce a tube having a high degree ofefiiciency as an oscillator or generator of micro-waves when operated inaccordance with the Barkhausen-Kurz principle, in which connection thestructure, arrangement and function of the electrodes constitute animportant part in determining the frequency of the oscillations.

The invention also contemplates .an improved transmission circuit andsystem of frequency stabilization for operation with such a tube.

Other objects and advantages will appear as the description proceeds.

The invention will now be described with reference to the accompanyingdrawing, in which:

Fig. 1 is a sectional View of a micro-ray tube constructed in accordancewith the invention, taken along the longitudinal axis of its electrodes;

Fig. 2 is a sectional View taken transversely along the axis of theelectrodes; and

Fig. 3 is a diagrammatic view of a tube and suitable transmission linefor operation therewith.

In the tube here shown by way of example, the numeral I designates anenvelope of glass or other suitable material, which encompasses a highlyevacuated chamber in which the electrode system is disposed. Theelectrode system comprises a filament or cathode 2, here shown as astraight filament supported upon lead wires 3 and 4, and at one end asuitable spring element 5 is provided to keep the filament under tensionand prevent sagging. In practice the filament under tension determines astraight line which may be regarded as coincident with the axis of thetube. Disposed concentrically about the filament as an axis is a helicalgrid 6, and concentric therewith a multiple plate electrode is provided,which is here shown as comprising three sections 1, 8 and 9. The grid 6is connected to and supported by outgoing leads l0 and H for externalcircuit connection. The sections l, 8 and 9 of said plate electrode areconnected to leads [2, l3 and M, respectively, which are also suitablyextended through the envelope for external circuit connection.

Under operating conditions, it has been found highly desirable to beable to place different D. C. potentials on the three sections of theplate electrode. This constitutes an important advantage of the presentinvention. In practice the two end sections of the plate are usuallyheld at one potential and the inner section is held at a differentpotential. However, it is possible togenerate 23.5 centimeteroscillations holding all plate sections at the same D. C. potential, sayfor example 20 volts. By making the central or inner plate section 120volts negative with respect to filament, the power output of the tubeincreases by a factor of four. Such an adjustment is not possible wherethe plate electrode is a unitary structure.

The ability to hold the various sections of the three section plateelectrode at desired potential differences with respect to filament, andhence with respect to each other, has been found very valuable in makingpossiblethe generation of any wave length in a desired range. Inoperating a tube constructed in accordance with the invention, it waspossible to go to the higher frequencies by holding the central platesection slightly negative with respect to filament, and then holding theoutside plate sections .at a still highernegative potential differencewith respect to filament. It is possible with this tube to generate anywave length between such ranges as from 50 to centimeters by changes inthe plate voltage. Thus, a decided superiority over prior art devices issecured in afiording a flexible control of wave length.

Fig. 3 is a diagrammatic showing of a circuit system in which a tube inaccordance with the invention is connected in operative relation. Asthere shown, it will be noted that the tube is used with a four wiretuned transmission line, one pair of wires i5 and it being connected tothe helical grid, and the second pair 57 and is being connected to theend sections 1 and 9 of the plate electrode. Bars or connections I9 and26 short circuit said plate and grid lines, respectively. Plate and gridvoltages are brought in as at 2| and 22, located at mid-point of saidbars. Vary- 5 maximum power output from the tube are given byway ofexample, as follows:

Eg: +200 volts, I milliamperes, Ir=3.2 amperes, Ep (inner): volts, andEp (outer) 20 volts The end sections of the plate electrode are permitedto undergo certain potential variations and the extent of thesevariations is subject to adjustment by varying the length of the platetransmission line. For example, in order to obtain the maximum amount ofpower from the tube over a range of frequencies, it has been foundadvantageous to adjust the length of the plate transmission line so thatit is an integral number of half wave lengths plus or minus a smalldistance-usually less than 1.0 centimeter. In certain prior art deviceswhere the plate is one cylindrical piece of metal and extends the fulllength of the grid, it is of necessity an equipotential surface inrelation to the grid. A material advantage in favor of the presentinvention arises from the fact that the outer or end sections of themultiple plate electrode may be caused to undergo potential variationssubject to control, thereby increasing the power output of the tube overa relatively wide frequency range.

At this point, it appears desirable to discuss the theory of operationof this tube, which is designed for use as an oscillator in theBarkhausen-Kurz as opposed to the conventional connection. In theconventional connection, the plate is held positive with respect tofilament, the grid is usually held negative with respect to filament,the voltage on the grid, 1. e., the alter nating component of voltage onthe grid is out of phase with the voltage on the plate, both plate andgrid are equi-potential electrodes, and frequency of oscillation isdetermined by the inductance and capacity of the associated circuit. Inthe Barkhausen-Kurz connection the grid is held highly positive withrespect to filament, the plate is usually held slightly negative withrespect to filament, the grid and plate may or may not be equipotentialelectrodes as the case may be, and frequency of oscillation isdetermined in part by tube geometry, i. e., radius of grid and plate, inpart by the D. C. voltages impressed on the electrodes, and in part bythe constants of an associated circuit, usually a section oftransmission line. For certain tubes of this type, the frequencygenerated is approximately that of an electron oscillating in theinter-electrode spaces back and forth through the meshes of the grid,being attracted by the positive grid and repelled by the negativefilament and plate. The mass of the electrons and the electric forces towhich they are subjected together determine frequency. In the specialtube with which we are here concerned, the grid itself is a resonatingelement and supports a radio-frequency difierence of potential along thedirection of its length at the particular frequency at which the gridhelix is tuned by virtue of its own distributed capacity and inductance.This arrangement gives substantially two tubes in one envelope in whichthe elements may be regarded as isolated from each other electrically bythe grid helix. As fully herein disclosed, the tube of the presentinvention proposes a three sectional plate electrode rather than a oneor two sectional plate. As previously explained, it is possible to holdthe central plate section highly negative with respect to filament, thusconfining the oscillating electrons to the ends of the grid.

Output power is increased by a factor of four by adjusting the voltageon the inner plate section from minus 20 volts--where it equals that onthe outer plate sections-to minus 120 volts. Since the central portionof the grid is at a voltage node, electrons in this portion of the tubecontribute little or nothing to the maintenance of oscillations.

Further, in order to generate oscillation energy of maximum power, it isnecessary that the outer plate sections-where the action is localizedbeconnected together by an'impedance as low as can be realized. This isaccomplished in the present invention by making this essentialconnection through a transmission line one-half wave length long andshorted at its far end. Moreover, it has been found that a low impedancepath from one end to the other of the plate is one condition to be metfor generating oscillations of maximum amplitude. In the presentinvention, this condition is satisfied for one wave length, namely, thatfor which the transmission line is one-half wave length long. This givesthe tube of the present invention a high degree of wave length stabilityindependent of applied voltages. In the instance of this invention, thesection of transmission line is an essential link in the oscillatingsystem and at the same time is a highly tuned filter.

In a tube constructed and operated in accordance with the presentinvention, the path for radio-frequency currents may be traced asfollows: from one end-plate section, through the plate transmission lineto the second end plate section, through the electron stream to theportion of the grid nearest the second end-plate section, through thegrid transmission line to the remaining end portion of the grid and backthrough the electrode stream to the first endplate section. The functionof the resonating grid in combination with the highly negative centralplate section is to isolate one end of the tube from the other. In theideal case, the transmission lines furnish the only path for currentfrom one end of the grid to the other, or from one end of the plate tothe other. Due to the filter properties of the lines, such a path isfurnished at but one frequency.

Changes, modifications and alternative arrangements are contemplatedwithin the scope l of the invention as defined by the appended claims.

I claim:

1. In a discharge tube for producing high frequency oscillations, anelectrode system comprising a cathode, a grid and an anode, the grid andanode being disposed concentrically about the cathode as a longitudinalaxis, and said anode being divided into at least three electricallyseparated sections; means including said electrode system for producingoscillations, and means for impressing different biasing potentials uponsaid different sections whereby said oscillations are stabilized.

2. In an electric discharge device for producing micro-waveoscillations, an electrode system comprising a cathode, a grid and ananode, the grid and anode being concentrically disposed about thecathode as an axis, and said anode being divided into a central sectionand end sections; means including said electrode system for producingoscillations, and means for impressing different biasing potentials uponsaid different sections, said grid being adapted to oscillate at thefrequency of said oscillations, whereby said oscillations arestabilized.

3. In a discharge tube for producing high frequency oscillations, anelectrode system comprising a cathode, a grid and an anode, the grid andanode being disposed concentrically about the cathode as a longitudinalaxis, and said anode being divided transversely into at least threeelectrically separated sections; means including said electrode systemfor producing oscillations, and means for impressing difierent biasingpotentials upon said different sections whereby said oscillations arestabilized.

4. In a discharge tube for producing high frequency oscillations, anelectrode system comprising a cathode, a grid and an anode, the grid andanode being disposed concentrically about the cathode as a longitudinalaxis, and said anode being divided transversely into at least threeelectrically separated sections; means including said electrode systemfor producing oscillations, and means for impressing upon the centralsection a biasing potential which is negative with respect to thebiasing potential upon said end sections.

5. In a system for generating high frequency oscillations, a spacedischarge tube having an electrode system, comprising a cathode, aresonating grid, and an anode divided transversely thereof into acentral section and end sections, said sections being electricallyseparated from one another; means for maintaining the said centralsection at a difference of potential with respect to the said endsections such as to produce oscillations in said electrode system; atuned transmission line connected to the free ends of said grid; andmeans for varying the electrical wave length of said line with respectto the desired operating frequency.

6. In a micro-wave generating system of the character described, amicro-wave tube having an electrode system, comprising a cathode, aresonating grid, and an anode divided transversely thereof into at leastthree electrically separated sections; a tuned transmission lineconnected across the end sections of said anode; and means for varyingthe voltage differential of the two end sections of said anode withrespect to the central section for the purpose of stabilizing thefrequency output of the system.

'7. In a system for generating high frequency oscillations, a micro-wavetube having an electrode system including a cathode, a resonating gridand an anode, said anode being divided transversely thereof into acentral section and two end sections all electrically insulated from oneanother; separate transmission lines connected across the end sectionsof said anode and the free ends of said grids, respectively; and meansincluding a voltage source for varying the voltage difierential of theend sections with respect to the central section, all of said sectionsbeing held negative relative to said cathode.

8. In a system for generating high frequency oscillations, a micro-Wavetube having an electrode system, including a cathode, a resonating grid,and an anode, said anode being divided transversely thereof into acentral section and two end sections all electrically insulated from oneanother; a tuned transmission circuit operatively connected to saidelectrode system; means in said circuit including sources of voltage formaintaining difierent polarizing potentials upon said grid and saidanode with respect to the cathode, the said central section and said endsections of the anode being held at negative potential with respect tothe cathode and at varying voltage levels with respect to each otherwhereby said end sections are electrically isolated from one another.

9. In a system for generating high frequency oscillations, a spacedischarge tube comprising an evacuated container and an electrode systemtherein, including a cathode, a resonating grid and a cylindrical plate,the grid and plate being disposed about the cathode as a longitudinalaxis, and said plate being divided transversely into a central sectionand end sections electrically insulated from one another; a transmissioncircuit operatively coupling the electrode system, and including a pairof transmission lines connecting said end sections of the plateelectrode; a pair of grid transmission lines connected to the terminalsof the grid electrode; shorting bars comiecting the ends of said plateand grid transmission lines, respectively; means in said circuitincluding voltage sources for maintaining different polarizingpotentials upon said grid and said plate electrode, plate and gridvoltages being applied at midpoints of said plate and grid shortingbars, respectively, the said central section and said end sections ofthe plate being held at negative potential with respect to the cathodeand at varying voltage levels with respect to each other.

. 10. In an electron discharge device of the.

character described, an electrode system comprising a cathode, aresonating grid being held at positive potential with respect to thecathode, and an anode, said anode being divided into at least threeelectrically separated sections, and means for impressing differentelectrical potentials thereon, one of said sections being held at anegative potential relatively high with respect to said cathode.

11. In a micro-wave tube, an electrode system comprising a cathode, aresonating grid held at positive potential with respect to the cathode,and a multiple anode divided into electrically separated sections; andmeans for varying and controlling the voltage diiferential of saidsections, including a voltage source for impressing a potential highlynegative relative to the cathode upon one section, while impressing alower value of negative potential with respect to the cathode uponothers of said sections.

WILLIAM D. HERSHBERGER.

